Liquid discharge head and liquid discharge apparatus including the same

ABSTRACT

A liquid discharge head is provided. The liquid discharge head includes: a semiconductor substrate including a first pressure chamber; an insulating film disposed above the semiconductor substrate; a first piezoelectric element disposed on an opposite side to the first pressure chamber of the insulating film and having a piezoelectric layer and a first and second electrode; and a doped layer formed in the semiconductor substrate. The doped layer partitions at least part of the first pressure chamber and has a lower electrical resistivity than the insulating film and the semiconductor substrate. A through hole having a conductor disposed on its inside is formed in the insulating film, and the first electrode and the doped layer are electrically continuous via the conductor.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2017-070055 filed on Mar. 31, 2017, the disclosures of which isincorporated herein by reference in its entirety.

BACKGROUND Field of the Invention

The present teaching relates to a liquid discharge head that dischargesliquid such as ink toward a medium, and relates also to a liquiddischarge apparatus that includes said liquid discharge head.

Description of the Related Art

There is known as a liquid discharge apparatus an ink-jet head of anink-jet printer, that while moving relatively to a recording medium,discharges ink onto the recording medium to form an image. For example,an ink-jet head that includes a nozzle plate, a channel substrate, and aplurality of piezoelectric elements, is publicly known. The nozzle platehas a plurality of nozzles formed therein. The channel substrate isformed by a silicon single crystal substrate, and is joined to thenozzle plate. The channel substrate has formed therein a plurality ofpressure chambers respectively communicating with the plurality ofnozzles and a manifold that supplies ink to the plurality of pressurechambers. An upper surface of the channel substrate has formed thereinan insulating film configured from silicon dioxide formed by performingheat treatment on the silicon single crystal substrate. The plurality ofpiezoelectric elements are disposed respectively corresponding to theplurality of pressure chambers, on the insulating film formed in theupper surface of the channel substrate.

When a semiconductor substrate such as a silicon single crystalsubstrate is employed as the channel substrate as in the above-describedink-jet head, the ink-jet head can be manufactured applying asemiconductor manufacturing process. As a result, an ink-jet head whichis small-sized and has a high disposing density of nozzles can bemanufactured cheaply. However, in this kind of ink-jet head, a thicknessof the insulating film partitioning the piezoelectric element and ink inthe pressure chamber is configured to be extremely thin, and a cracksometimes occurs in an elastic film in the process of manufacturing theink-jet head.

SUMMARY

In the above-mentioned ink-jet head, when a crack has occurred in theinsulating film, there is a possibility that as will be mentioned later,ink in the pressure chamber enters the crack causing the ink and a lowerelectrode to short-circuit.

An object of the present teaching is that even when a crack has occurredin an insulating film of an ink-jet head, it is prevented that ink in apressure chamber enters the crack causing a lower electrode and the inkto short-circuit.

An aspect of the present teaching, there is provided a liquid dischargehead including: a semiconductor substrate including a first pressurechamber; an insulating film disposed above the first pressure chamber; afirst piezoelectric element disposed on an opposite side to the firstpressure chamber of the insulating film, in a first direction in whichthe first pressure chamber and the insulating film overlap, the firstpiezoelectric element including: a first electrode disposed above theinsulating film, a piezoelectric layer disposed above the firstelectrode, and, a second electrode disposed above the piezoelectriclayer. A semiconductor substrate further includes a doped layer, whereinthe doped layer defines at least part of the first pressure chamber. Thedoped layer has a lower electrical resistivity than the insulating filmand the semiconductor substrate. The insulating film includes a throughhole in which a conductor is disposed, and the first electrode and thedoped layer are electrically connected to the conductor disposed in thethrough hole.

Due to the above-described configuration, a doped layer whose electricalresistivity is lower than those of a semiconductor substrate and aninsulating film is formed in the semiconductor substrate. Since thisdoped layer partitions at least part of a pressure chamber, a liquidfilled into the pressure chamber can electrically contact the dopedlayer. Moreover, the doped layer is connected to a first electrode of afirst piezoelectric element via a conductor disposed in a through hole.Therefore, the first electrode and the liquid filled into the pressurechamber are electrically connected via the doped layer and the conductordisposed in the through hole. As a result, by performing grounding, andso on, of the first electrode to keep it at a constant potential, apotential of the liquid in the pressure chamber can be easily set to aconstant potential. Therefore, even when a crack has occurred in theinsulating film of a liquid discharge head, it can be suppressed thatink in the pressure chamber enters the crack, and it can be preventedthat the ink and a piezoelectric element short-circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view depicting an outline of an ink-jet printer Iaccording to the present embodiment.

FIG. 2 is a schematic top view of one head unit 16 of an ink-jet head.

FIG. 3 is a schematic top view depicting a state where piezoelectricelements 44, wirings 45, a protective film 46, drive contacts 53, andground contacts 54, of the head unit 16 depicted in FIG. 2 have beenremoved.

FIG. 4 is an enlarged view of section A of FIG. 2.

FIG. 5 is a view depicting a state where the protective film 46, thewirings 45, the drive contacts 53, and the ground contacts 54 have beenremoved from FIG. 4.

FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 4.

FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 4.

FIG. 8 is a cross-sectional view taken along the line VIII-VIII of FIG.4.

FIG. 9A is a view depicting a deposition step of an insulating film;FIG. 9B is a view depicting a deposition step of a doped layer; FIG. 9Cis a view depicting a formation step of a hole for continuity of thedoped layer and a common electrode; FIG. 9D is a view depicting adeposition step of the common electrode; and FIG. 9E is a view depictinga deposition step of a piezoelectric material film.

FIG. 10A is a view depicting a formation step of a conductive film foran individual electrode; FIG. 10B is a view depicting a formation stepof the individual electrode; and FIG. 10C is a view depicting an etchingstep of the piezoelectric material film.

FIG. 11A is a view depicting a deposition step of a protective film; andFIG. 11B is a view depicting a step of hole formation for continuity ofthe individual electrode and a wiring.

FIG. 12A is a view depicting a deposition step of a conductive film forthe wiring; FIG. 12B is a view depicting an etching step (wiringformation step) of the conductive film for the wiring; and FIG. 12C is aview depicting a partial removal step of the protective film.

FIG. 13A is a view depicting a polishing step of a channel substrate;FIG. 13B is a view depicting an etching step (formation step of apressure chamber, a channel, and a common liquid chamber) of the channelsubstrate; and FIG. 13C is a view depicting a joining step of a nozzleplate.

FIG. 14 is a schematic explanatory view of the doped layer including aregion having two kinds of ion concentrations.

FIG. 15 is a view corresponding to FIG. 2 of a head unit 16A having apiezoelectric layer provided commonly to pressure chamber columns 25.

FIG. 16 is a view corresponding to FIG. 7 depicting a case where athrough hole 251 has been provided between two pressure chambers 26 in aconveyance direction.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present teaching will be described. FIG. 1 is aplan view depicting an outline of an ink-jet printer 1 according to thepresent embodiment. Each of directions of front, rear, left, and rightdepicted in FIG. 1 are defined as “front”, “rear”, “left”, and “right”of the ink-jet printer 1. Moreover, this side of the paper surface isdefined as “up”, and the far side of the paper surface is defined as“down”.

<Schematic Configuration of Printer>

As depicted in FIG. 1, the ink-jet printer 1 mainly includes a platen 2,a carriage 3, a carriage drive mechanism 4, an ink-jet head 5, aconveyance mechanism 6, a controller 7, and an ink supply unit 8.

A recording sheet 100 which is a recording medium is placed on an uppersurface of the platen 2. The carriage 3 is configured so as to makereciprocating movement in a left-right direction (hereafter, also calleda scanning direction) along two guide rails 10, 11 in a region facingthe platen 2, by the carriage drive mechanism 4. The carriage drivemechanism 4 includes: a belt 12; two rollers 13 disposed so as tosandwich the platen 2 on both sides in the scanning direction of theplaten 2; and a carriage drive motor 14. The belt 12 is coupled to thecarriage 3. The belt 12 is stretched around so as to form anelliptically shaped loop long in the scanning direction when viewed fromabove, between the two rollers 13 disposed separated in the scanningdirection. As depicted in FIG. 1, the roller 13 on a right side iscoupled to a rotating shaft of the carriage drive motor 14. By rotatingthe carriage drive motor 14, the belt 12 can be circulated around thetwo rollers 13. Consequently, the carriage 3 coupled to the belt 12 canbe caused to make reciprocating movement in the scanning direction.

The ink-jet head 5 is attached to the carriage 3 and moves in thescanning direction along with the carriage 3. The ink-jet head 5includes four head units 16 aligned in the scanning direction. Moreover,the ink supply unit 8 includes: four ink cartridges 17 in which inks offour colors (black, yellow, cyan, magenta) have been respectivelystored; a cartridge holder 18 fitted with the four ink cartridges 17;and unillustrated tubes. The four head units 16 and the four inkcartridges 17 are respectively connected via the unillustrated tubes. Asa result, the inks of the four colors are supplied from the ink supplyunit 8 to the four head units 16.

A plurality of nozzles 24 are formed in a lower surface (a surface onthe far side of the paper surface of FIG. 1) of each of the head units16 (refer to FIG. 3). The nozzles 24 of each of the head units 16discharge toward the recording sheet 100 placed on the platen 2 the inksupplied from the ink cartridge 17.

The conveyance mechanism 6 has two conveyance rollers 18, 19 disposed soas to sandwich the platen 2 in a front-rear direction. The conveyancemechanism 6 conveys the recording sheet 100 placed on the platen 2frontwards (in what is hereafter also called a conveyance direction) bythe two conveyance rollers 18, 19.

The controller 7 includes the likes of a ROM (Read Only Memory), a RAM(Random Access Memory), and an ASIC (Application Specific integratedCircuit) that includes a control circuit. The controller 7 executesvarious kinds of processing, such as printing, on the recording sheet100, by the ASIC, according to a program stored in the ROM. For example,in a printing processing, the controller 7 controls the likes of theink-jet head 5 or carriage drive motor 14 to print an image on therecording sheet 100, based on a printing instruction inputted from anexternal apparatus such as a PC. Specifically, the controller 7 causesan ink discharge operation and a conveyance operation to be alternatelyperformed. The ink discharge operation discharges ink while moving theink-jet head 5 along with the carriage 3 in the scanning direction, andthe conveyance operation conveys a certain amount of the recordingsheets 100 in the conveyance direction by the conveyance rollers 18, 19.

Next, a configuration of the head unit 16 of the ink jet head 5 will bedescribed. Note that since the four head units 16 of the ink-jet head 5all have the same configuration, a description of one of those four headunits 16 will be made, and descriptions of the other head units 16 willbe omitted.

The head unit 16 mainly includes a nozzle substrate 20, a channelsubstrate 21, an insulating film 30, a piezoelectric element 44, awiring 45, and a protective film 46 (refer to FIG. 6). In thedescription below, the nozzle substrate 20, the channel substrate 21,and the insulating film 30 of the head unit 16, and an ink channelformed on an inside of the channel substrate 21, will be described. Notethat FIG. 2 is a schematic top view of the head unit 16. In order tosimplify the drawing, FIG. 2 omits illustration of the later-describednozzle 24. FIG. 3 is a schematic top view depicting a state where thepiezoelectric element 44, the wiring 45, and the protective film 46, ofthe head unit 16 depicted in FIG. 2 have been removed. FIG. 4 is a viewenlarging a portion of a frame line A of FIG. 2. FIG. 5 is a viewdepicting a state where the protective film 46 has been removed fromFIG. 4 in order to simplify the drawing.

<Nozzle Substrate 20>

The nozzle substrate 20 is a silicon single crystal substrate. Note thatthe nozzle substrate 20 can also be formed by the likes of a metalmaterial such as stainless steel, or a synthetic resin material such aspolyimide. As depicted in FIGS. 6 and 7, the plurality of nozzles 24 areformed in the nozzle substrate 20. Moreover, as depicted in FIG. 3, theplurality of nozzles 24 configure a nozzle column 25 arranged in theconveyance direction with an arrangement pitch P, and two of such nozzlecolumns 25 are formed. The two nozzle columns 25 are disposed aligned inthe scanning direction. Moreover, positions of the nozzles 24 in theconveyance direction are misaligned by half of the arrangement pitch Pof each of the nozzle columns 25 (P/2), between the two nozzle columns25.

<Channel Substrate 21>

The channel substrate 21 is a silicon single crystal substrate. Asdepicted in FIG. 3, the following are formed in the channel substrate21, namely: a plurality of pressure chambers 26 that respectivelycommunicate with the plurality of nozzles; a common liquid chamber 28;and a plurality of channels 29 that communicate the plurality ofpressure chambers 26 and the common liquid chamber 28. The plurality ofpressure chambers 26 configure a pressure chamber column 27 arranged inthe conveyance direction, and two of such pressure chamber columns 27are formed. These two pressure chamber columns 27 are aligned in thescanning direction. Each of the pressure chambers 26 has a substantiallyrectangular shape long in the scanning direction in top view. The commonliquid chamber 28 is provided between the two pressure chamber columns27 in the scanning direction. The common liquid chamber 28 has asubstantially rectangular shape long in the conveyance direction in topview. A rear end section in the conveyance direction, of the commonliquid chamber 28 is positioned even more rearwards than those of thetwo pressure chamber columns 27. Similarly, a front end section in theconveyance direction, of the common liquid chamber 28 is positioned evenmore frontwards than those of the two pressure chamber columns 27. Asdepicted in FIG. 3, a supply port 28 a for supplying ink to inside thecommon liquid chamber 28 is provided between a rear end of the commonliquid chamber 28 and the most rearward positioned pressure chamber 26in the conveyance direction (the front-rear direction). Ink from the inkcartridge 17 is supplied, via the unillustrated tube, to the supply port28 a.

As depicted in FIGS. 3 to 5, the channel 29 is formed between the commonliquid chamber 28 and each of the pressure chambers 26. A liquid in thecommon liquid chamber 28 is supplied to each of the pressure chambers 26via the channel 29.

FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 4,and depicts a cross-sectional view of the pressure chamber 26. FIG. 8 isa cross-sectional view taken along the line VIII-VIII of FIG. 4, anddepicts a cross-sectional view of the channel 29. By looking at FIGS. 7and 8, it may be understood that a width (a length in the conveyancedirection) of the channel 29 is configured narrower than a width of thepressure chamber 26. Since the width of the channel 29 is configurednarrower than the width of the pressure chamber 26 in this way, achannel resistance of the channel 29 can be increased. It is suppressedthat a pressure wave generated in ink in the pressure chamber 26 escapesto the common liquid chamber 28 when, as will be mentioned later, thepiezoelectric element 44 and the insulating film 30 cooperate to applypressure to the ink in the pressure chamber 26.

As depicted in, for example, FIG. 6, the insulating film 30 is formed ona channel substrate 21 upper surface. Now, the insulating film 30 isformed over an entire upper surface of the channel substrate 21, and theplurality of pressure chambers 26 are covered by the insulating film 30(refer to FIG. 3). In the present embodiment, the insulating film 30 isa silicon dioxide (SiO₂) film formed by oxidizing a surface of thesilicon channel substrate 21. Note that the insulating film 30 may be asilicon nitride (SiNx) film formed by nitridizing the surface of thesilicon channel substrate 21. Note that the insulating film 30 is notlimited to being formed by oxidizing or nitridizing the surface of thesilicon channel substrate 21. The insulating film 30 need only be formedas a film of an insulator, and can also be formed by depositing the filmof the insulator on the upper surface of the channel substrate 21 by apublicly known deposition technology such as sputtering. Moreover, theinsulating film 30 need not necessarily be a single layer film, and maybe a film formed by a plurality of layers.

Furthermore, a doped layer 32 formed by doping the channel substrate 21with an impurity ion such as a sodium ion, for example, is formed on alower side of the insulating film 30, of the channel substrate 21. Thedoped layer 32 is formed on the lower side of the insulating film 30(refer to FIG. 6). Moreover, because the doped layer 32 is located onthe lower side of the insulating film 30, the doped layer 32 is formedover an entire region of the upper surface of the channel substrate 21and has the same shape as the insulating film 30 in top view, althoughthis is not depicted in FIG. 3. An upper surface of the pressure chamber26 is covered by the doped layer 32, and an upper surface of the dopedlayer 32 is further covered by the insulating film 30 (refer to FIG. 6).Note that as will be mentioned later, the doped layer 32 is a regionwhose conductivity has been raised as a result of the silicon channelsubstrate 21 having been doped with the impurity ion, and resistivity(specific resistance) of the doped layer 32 is configured lower thanresistivity of the silicon configuring the channel substrate 21.

<Piezoelectric Element 44>

The plurality of piezoelectric elements 44 are provided respectivelycorresponding to the plurality of pressure chambers 26. Each of thepiezoelectric elements 44 cooperates with the insulating film 30 tochange a capacity of a corresponding pressure chamber 26. As a result,each of the piezoelectric elements 44 cooperates with the insulatingfilm 30 to apply pressure to ink in the corresponding pressure chamber26 and thereby provide the ink with energy for discharging the ink fromthe nozzle 24 communicating with said pressure chamber 26. As depictedin, for example, FIGS. 6 and 7, the plurality of piezoelectric elements44 are respectively disposed above each of the pressure chambers 26, onthe upper surface of the above-mentioned insulating film 30. Thepiezoelectric element 44 has a common electrode (lower electrode) 41, apiezoelectric layer 42, and an individual electrode (upper electrode)43.

A configuration of the piezoelectric element 44 will be described below.The plurality of piezoelectric elements 44 are disposed so as torespectively face the plurality of pressure chambers 26, sandwiching theinsulating film 30 and the doped layer 32. Note that as depicted in FIG.2, the plurality of piezoelectric elements 44 configure two columns ofpiezoelectric elements 44 arranged in the conveyance direction accordingto an arrangement of the pressure chambers 26, and these two columns ofpiezoelectric elements 44 are aligned in the scanning direction.

The common electrode 41 is formed on the upper surface of the insulatingfilm 30 so as to cover the whole of the insulating film 30. Althoughillustration of the common electrode 41 is omitted in FIG. 3, the commonelectrode 41 has substantially the same shape as the insulating film 30in top view. The common electrode 41 need only be formed by a materialhaving conductivity, and a material of the common electrode 41 is notparticularly limited. For example, one having a two layer structure ofplatinum (Pt) and titanium (Ti) may be adopted.

The piezoelectric layers 42 are respectively disposed in portionsoverlapping the plurality of pressure chambers 26 in the up-downdirection, of an upper surface of this common electrode 41. Thepiezoelectric layer 42 is configured by a piezoelectric material whoseprincipal component is lead zirconate titanate (PZT) which is a mixedcrystal of lead titanate and lead zirconate. Alternatively, thepiezoelectric layer 42 may be formed by a non-lead based piezoelectricmaterial not containing lead.

As mentioned above, FIG. 4 is a view enlarging the portion of the frameline A of FIG. 2, and FIG. 5 is a view depicting a state where theprotective film 46, a drive contact 53, and a ground contact 54 havebeen removed from FIG. 4 in order to simplify the drawing. Note thatFIG. 5 also omits illustration of the nozzle 24 and a continuity section52. As depicted in FIGS. 4 and 5, each of the piezoelectric layers 42has a substantially rectangular shape in top view.

As depicted in FIG. 5, a right end section 42R of each of thepiezoelectric layers 42 is positioned more to a right side than a rightend section 26R of a corresponding pressure chamber 26 in the scanningdirection (the left-right direction). Moreover, a left end section 42Lof each of the piezoelectric layers 42 is positioned more to a left sidethan a left end section 26L of the corresponding pressure chamber 26 inthe scanning direction, and extends to a region overlapping the commonliquid chamber 28 in the up-down direction. In other words, the left endsection 42 of each of the piezoelectric layers 42 is positioned more tothe left side than the channel 29 in the scanning direction. Moreover,in the conveyance direction (the front-rear direction), a rear end ofthe piezoelectric layer 42 is positioned more rearwards than a rear endof the corresponding pressure chamber 26, and a front end of thepiezoelectric layer 42 is positioned more frontwards than a front end ofthe corresponding pressure chamber 26 and the channel 29 communicatingwith this corresponding pressure chamber 26. Thus, a length in theconveyance direction of each of the piezoelectric layers 42 is longerthan a length in the conveyance direction of the pressure chamber 26.Moreover, a length in the scanning direction of each of thepiezoelectric layers 42 is longer than a length in the scanningdirection of the pressure chamber 26. Moreover, each of thepiezoelectric layers 42 is disposed so as to cover the correspondingpressure chamber 26 and the channel 29 communicating with thatcorresponding pressure chamber 26.

As depicted in FIGS. 4 and 5, a plurality of the individual electrodes43 are formed in positions respectively corresponding to the pluralityof pressure chambers 26, on an upper surface of each of thepiezoelectric layers 42. The individual electrode 43 has a rectangularplanar shape which is a size smaller than that of the pressure chamber26. The individual electrode 43 is formed by the likes of platinum (Pt)or iridium (Ir), for example.

As depicted in FIG. 5, in the conveyance direction, a rear end of theindividual electrode 43 is positioned more frontwards than a rear end ofa corresponding pressure chamber 26, and a front end of the individualelectrode 43 is positioned more rearwards than a front end of thecorresponding pressure chamber 26. Moreover, in the scanning direction,a left end 43L, of the individual electrode 43 is positioned more to theright side than the left end 26L, of the pressure chamber 26, and aright end 43R of the individual electrode 43 is positioned more to theright side than the right end 26R of the pressure chamber 26. Thus, theleft end 26L of the pressure chamber 26 and the channel 29 are locatedbetween the left end 42L of the piezoelectric layer 42 and the left end43L, of the individual electrode 43 in the scanning direction. The rightend 26R of the pressure chamber 26 is located between the right end 42Rof the piezoelectric layer 42 and the right end 43R of the individualelectrode 43 in the scanning direction.

Note that the insulating film 30 is disposed between the previouslymentioned doped layer 32 and common electrode 41. As depicted in FIGS. 4and 5, in top view, through holes 51 are respectively formed inpositions between two channels 29 in the conveyance direction andsandwiched by the pressure chamber 26 and the common liquid chamber 28in the scanning direction. As depicted in FIG. 6, the through hole 51 isa through hole penetrating the insulating film 30, and one of thepiezoelectric layers 42 is disposed above each of the through holes 51.Moreover, an inside of each of the through holes 51 is filled with aconductive material. As a result, the doped layer 32 and the commonelectrode 41 are electrically continuous via the conductive material onthe inside of each of the through holes 51. As will be mentioned later,the common electrode 41 is held at ground potential, hence a potentialof the doped layer 32 is also held at ground potential.

Furthermore, as depicted in, for example, FIGS. 6 to 8, the protectivefilm 46 is formed so as to cover the plurality of piezoelectric elements44 and the insulating film 30. Note that as depicted in FIGS. 2 and 4,the protective film 46 is formed over substantially the entire region ofthe upper surface of the channel substrate 21. The protective film 46prevents moisture included in the air from infiltrating into thepiezoelectric layer 42. The protective film 46 is formed by a materialhaving water resistance, such as alumina (A1 ₂O₃). Alternatively, theprotective film 46 may be formed by silicon dioxide (SiO₂).

Note that in order to lessen hindrance to deformation of thepiezoelectric layer 42 due to the protective film 46, a rectangularshaped opening 46 a is formed in a portion overlapping the individualelectrode 43 formed on the upper surface of the piezoelectric layer 42,of the protective film 46, when viewed from a thickness direction of theprotective film 46 (refer to FIGS. 4 and 6). As depicted in FIG. 4, theopening 46 a is formed so as to be a size smaller than the individualelectrode 43. As a result, substantially all of a portion excluding anouter peripheral portion of the individual electrode 43 is exposed fromthe protective film 46. Note that on an inner side of the opening 46 a,the piezoelectric layer 42 is not covered by the protective film 46.However, because the piezoelectric layer 42 is covered by the individualelectrode 43 in said portion, infiltration of moisture into thepiezoelectric layer 42 from outside is suppressed.

The protective film 46 functions additionally as a film of an insulator.The continuity section 52 disposed so as to penetrate the protectivefilm 46 is provided in a portion covering an end section on a right sideof each of the individual electrodes 43, of the protective film 46(refer to FIGS. 4 and 6). Moreover, as depicted in FIGS. 4 to 6, thewirings 45 extending toward the right side respectively extend from thecontinuity sections 52 provided in each of the piezoelectric elements44. Although FIG. 2 omits illustration of the continuity sections 52,FIG. 2 does illustrate that the wirings 45 extend toward the right sidefrom the piezoelectric elements 44 disposed in a column corresponding tothe pressure chamber column 27 on the right side, of the two pressurechamber columns 27. These wirings 45 are referred to as wirings 45 a.addition, the wirings 45 extending toward the right side respectivelyextend also from each of the piezoelectric elements 44 disposed in acolumn corresponding to the pressure chamber column 27 on the left side,of the two pressure chamber columns 27. These wirings 45 are referred toas wirings 45 b. The wirings 45 b extend to the right side of FIG. 2passing between the piezoelectric elements 44 disposed in a columncorresponding to the pressure chamber column 27 on the right side.Moreover, a plurality of the drive contacts 53 are disposed aligned inthe conveyance direction on the protective film 46, in a right endsection of the channel substrate 21. The wirings 45 (the wirings 45 a,45 b) led out rightwards from the individual electrodes 43 (thecontinuity sections 52) are respectively connected to the drive contacts53. One end section (a left end section) of each of the wirings 45 isconnected to one of the continuity sections 52, and the other endsection (a right end section) of each of the wirings 45 is connected toone of the drive contacts 53. Each of the wirings 45 is continuous withthe individual electrode 43 via the continuity section 52. Moreover, twoof the ground contacts 54 are also disposed on both sides in theconveyance direction of the plurality of drive contacts 53, in the rightend section of the channel substrate 21. The ground contact 54 isconnected, via a continuity section (illustration of which is omitted)penetrating the protective film 46, to the common electrode 41 disposedon a lower side of the protective film 46. The wirings 45 a, 45 b, thecontinuity section 52, the drive contact 53, and the ground contact 54are formed by platinum (Pt), gold (Au), aluminum (Al), or the like.

As depicted in FIG. 2, a COF (Chip On Film) 50 which is a wiring memberis joined to an upper surface of the right end section of the channelsubstrate 21. Moreover, a plurality of wirings (not illustrated) formedin the COF 50 are respectively electrically connected to the pluralityof drive contacts 53 and the plurality of ground contacts 54. An endsection on an opposite side to the drive contacts 53, of the COF 50 isconnected to the controller 7 of the printer 1 (refer to FIG. 1).Moreover, the COF 50 is mounted with a driver IC 50A.

The driver IC 50A generates and outputs a drive signal for driving thepiezoelectric element 44, based on a control signal sent from thecontroller 7. The drive signal outputted from the driver IC 50A isinputted to the drive contact 53 via the wiring of the COF 50, and isfurther supplied to the individual electrode 43 via the wiring 45. Apotential of the individual electrode 43 supplied with the drive signalchanges between a certain drive potential and ground potential.Moreover, a ground wiring is also formed in the COF 50, and this groundwiring is electrically connected to the ground contact 54. As a result,a potential of the common electrode (the lower electrode) 41 connectedto the ground contact 54 is always maintained at ground potential.

Operation of the piezoelectric element 44 when the drive signal has beensupplied from the driver IC 50A will he described. In a state where thedrive signal is not supplied, the potential of the individual electrode43 is ground potential, and is the same potential as the commonelectrode 41. When, from this state, the drive signal is supplied to theindividual electrode 43 whereby the drive potential is applied to theindividual electrode 43, a potential difference occurs between thatindividual electrode 43 and the common electrode 41. As a result of thispotential difference, an electric field parallel to a thicknessdirection of the piezoelectric layer 42 acts on a portion sandwiched bythe individual electrode 43 and the common electrode 41, of thepiezoelectric layer 42. At this time, the piezoelectric layer 42 extendsin the thickness direction and contracts in a surface direction, due toa piezoelectric inverse effect. Furthermore, the insulating film 30bends convexly to a pressure chamber 26 side along with this contractiondeformation of the piezoelectric film. As a result, the capacity of thepressure chamber 26 decreases, whereby a pressure wave is generated inthe pressure chamber 26 and a droplet of ink is discharged from thenozzle 24 communicating with the pressure chamber 26.

Note that because the insulating film 30 is extremely thin, there is apossibility of a crack occurring in it in a manufacturing step of theinkjet head 5. When a crack has occurred in the insulating film 30,there is a risk that if ink in the pressure chamber 26 is positively ornegatively charged, the charged ink is attracted to the grounded commonelectrode 41 and thereby infiltrates into the crack. This is becausewhen ink in the pressure chamber 26 is positively or negatively charged,a potential of the ink is unstable and a potential difference sometimesoccurs between the ink and the common electrode 41. In such a case, thecharged ink sometimes infiltrates into the crack of the insulating film30, whereby the ink and the common electrode 41 of the piezoelectricelement 44 short-circuit. In that case, it becomes impossible for ink tobe discharged normally from the nozzle corresponding to thepiezoelectric element 44 that has short-circuited with the ink.Moreover, in some cases, the piezoelectric element 44 that hasshort-circuited with the ink may also sometimes be destroyed.

In contrast, in the present embodiment, as mentioned above, the uppersurface of the pressure chamber 26 is partitioned by the doped layer 32,and the doped layer 32 is electrically continuous with the commonelectrode 41 thereby being held at ground potential. Because ink in thepressure chamber 26 is in contact with the doped layer 32 partitioningthe upper surface of the pressure chamber 26, the ink is always held atground potential. As a result, charging of the ink can be suppressed,and the potential of the ink can be kept to the same as the potential ofthe common electrode 41. As a result, the ink in the pressure chamber 26can be prevented from being attracted to the common electrode 41 andthereby infiltrating into the crack. Note that the potential of thecommon electrode 41 need only be held at a constant potential and neednot necessarily be ground potential.

Next, manufacturing steps of the above-mentioned head unit 16 of theink-jet head 5 will be described particularly with reference to FIGS. 9Ato 13C.

First, as depicted in FIG. 9A, the insulating film 30 of silicon dioxideis deposited on a surface of the channel substrate 21 which is a siliconsubstrate. A publicly known deposition method can be employed as adeposition method of the silicon dioxide insulating film 30. Forexample, thermal oxidation treatment can be suitably adopted. Note thatthe insulating film 30 need not necessarily be of silicon dioxide. Theinsulating film 30 can be formed by a material other than silicondioxide, by any deposition method. Moreover, the insulating film 30 maybe formed as a multi-layer film.

Next, as depicted in FIG. 9B, an unillustrated ion implanting apparatusis employed to implant from the surface of the channel substrate 21 (asurface where the insulating film 30 has been formed, of the channelsubstrate 21) ions such as sodium ions and thereby form the doped layer32 on a lower side of the insulating film 30. Now, a standard ionimplanting apparatus includes: an ion source that generates an intendedion; an accelerator that accelerates the ion by an electric field; amass separator that selects only the intended ion; and a holder thatholds a target to be an object of implantation, and these are disposedinside a vacuum chamber. The channel substrate 21 is held in the holderinside the vacuum chamber, and the ion accelerated by the accelerator isimplanted in the channel substrate 21. A depth that the ion is implantedin the channel substrate 21 can be adjusted by adjusting an acceleratingvoltage of the accelerator. In the present embodiment, the acceleratingvoltage of the accelerator is adjusted such that the doped layer 32 isformed in a region contacting the insulating film 30, immediately on thelower side of the insulating film 30. Moreover, an amount of ionsimplanted per unit area is adjusted such that the doped layer 32 isformed with a uniform ion concentration. Note that the doped layer 32need not necessarily be formed using an ion implanting apparatus, andmay be formed by doping with an impurity ion using any publicly knownmethod.

Note that the above-mentioned step of depositing the insulating film 30and step of forming the doped layer 32 need not be performed in theabove-described order, and it is possible for the doped layer 32 to beformed first, after which the insulating film 30 is deposited. Forexample, it is also possible for the doped layer 32 to be formed usingthe ion implanting apparatus, after which the silicon dioxide insulatingfilm 30 is deposited by thermal oxidation treatment on the upper surfaceof the doped layer 32. Moreover, it is also possible for the doped layer32 to be formed by another publicly known method besides the methodemploying the ion implanting apparatus, after which the insulating film30 of silicon dioxide or another material is deposited on the uppersurface of the doped layer 32 using a publicly known deposition method.

Next, as depicted in FIG. 9C, the through hole 51 is formed in theinsulating film 30 by etching. This through hole 51 is a hole forrendering electrically continuous the doped layer 32 and the commonelectrode 41 to be formed on the insulating film 30 in the next step.Note that the through hole 51 is formed in a position that will overlapthe piezoelectric layer 42 when the piezoelectric layer 42 has beenformed in a later step.

Next, as depicted in FIG. 9D, the common electrode 41 is deposited bythe likes of sputtering, over an entire region of the upper surface ofthe insulating film 30. At this time, part of a conductive materialforming the common electrode 41 is filled into the through hole 51,whereby a continuity section that renders electrically continuous thecommon electrode 41 and the doped layer 32 is formed on an inner side ofthe through hole 51. Next, as depicted in FIG. 9E, a piezoelectricmaterial film 42A configured from a piezoelectric material such as PZTis deposited in an entire region of the upper surface of the commonelectrode 41 by the likes of a sol-gel method or sputtering.

Furthermore, the individual electrode 43 is formed on an upper surfaceof the piezoelectric material film 42A. First, as depicted in FIG. 10A,a conductive film 43A is deposited on the upper surface of thepiezoelectric material film 42A by the likes of sputtering. Then, asdepicted in FIG. 10B, etching is carried out on the conductive film 43A,whereby a plurality of the individual electrodes 43 are each formed onthe upper surface of the piezoelectric material film 42A.

As depicted in FIG. 10C, etching of the piezoelectric material film 42Ais performed to form the piezoelectric layer 42. As a result, theplurality of piezoelectric elements 44 are formed on the insulating film30.

Next, as depicted in FIG. 11A, the protective film 46 of silicon dioxideis deposited by sputtering or the like, so as to cover the plurality ofpiezoelectric elements 44 and the common electrode 41. Note that theprotective film 46 can also be deposited as a film configured fromsilicon nitride or another insulating material. Moreover, the protectivefilm 46 can also be formed as a multi-layered insulating film.

After the protective film 46 has been formed, a hole 56 is formed byetching, in a portion covering an end section of the individualelectrode 43, of the protective film 46, as depicted in FIG. 11B. Thishole 56 is a hole for rendering electrically continuous the individualelectrode 43 and the wiring 45 to be formed on the protective film 46 inthe next step.

Next, the plurality of wirings 45 are formed on the protective film 46.First, as depicted in FIG. 12A, a conductive film 145 is deposited, bysputtering or the like, on the upper surface of the protective film 46.At this time, part of a conductive material is filled into the hole 56,whereby the continuity section 52 that renders electrically continuousthe individual electrode 43 and the conductive film 145, is formed inthe hole 56. Next, as depicted in FIG. 12B, etching is carried out onthis conductive film 145, whereby unnecessary portions are removed andthe plurality of wirings 45 are respectively formed.

Next, as depicted in FIG. 12C, etching is performed on the protectivefilm 46 to remove portions covering the individual electrodes 43 of theplurality of piezoelectric elements 44, of the protective film 46. As aresult, the opening 46 a is formed in the protective film 46, wherebythe individual electrode 43 located below the opening 46 a is exposed.

Note that although not particularly required when the wiring 45 isformed by a stable material such as gold, it is preferable that when thewiring 45 is formed by aluminum, a wiring protective film covering thewiring 45 is provided for a purpose of corrosion prevention. In thiscase, it is possible for etching to be carried out on a conductive film45A to remove unnecessary portions and thereby form the plurality ofwirings 45, and then for a wiring protective film covering the pluralityof wirings 45 to be deposited by sputtering or the like. For example, awiring protective film configured from silicon dioxide or siliconnitride can be deposited. Moreover, in this case, it is possible thatwhen etching is performed on the protective film 46 to remove theportions covering the individual electrodes 43 of the plurality ofpiezoelectric elements 44, of the protective film 46, simultaneously,portions covering the individual electrodes 43 of the plurality ofpiezoelectric elements 44, of the wiring protective film are alsoremoved by etching.

Next, as depicted in FIG. 13A, the channel substrate 21 where the inkchannel is formed is removed, by polishing, from a lower surface side(an opposite side to the insulating film 30), and a thickness of thechannel substrate 21 is thinned to a certain thickness. Although athickness of a silicon wafer from which the channel substrate 21originates is about 500 μm to 700 μm, in this polishing step, thethickness of the channel 21 is thinned to about 100 μm.

After the above-described polishing, etching is performed from the lowersurface side on the opposite side to the insulating film 30, of thechannel substrate 21, as depicted in FIG. 13B, whereby the plurality ofpressure chambers 26, the common liquid chamber 28, and the channels 29are formed. Note that this etching of the channel substrate 21 may bewet etching or dry etching. Note that when forming the pressure chamber26, etching is performed on the channel substrate 21 to a depth that thedoped layer 32 is exposed. Moreover, as depicted in FIG. 13C, the nozzleplate 20 in which the plurality of nozzles 24 have been formed is joinedby an adhesive agent to the lower surface of the channel substrate 21,at a certain position,

In the embodiment described above, the channel substrate 21 correspondsto a “semiconductor substrate” of the present teaching, and theinsulating film 30 corresponds to an “insulating film” of the presentteaching. The piezoelectric element 44 corresponds to a “firstpiezoelectric element” and a “second piezoelectric element” of thepresent teaching. The doped layer 32 corresponds to a “doped layer” ofthe present teaching. The through hole 51 corresponds to a “through holehaving a conductor disposed on its inside” of the present teaching.

Next, modified modes where various changes have been made to thepreviously described embodiment will be described. However,configurations of the modified modes similar to those of the previouslydescribed embodiment will be assigned with the same symbols as thoseassigned in the previously described embodiment, and descriptionsthereof will be appropriately omitted. Note that the modified modesdepicted below are merely exemplifications, and the present teaching isnot limited to these. Moreover, the modified modes below may also beappropriately combined.

In the previously described embodiment, when forming the doped layer 32,the amount of ions implanted per unit area was adjusted such that thedoped layer 32 was formed with a uniform ion concentration. However, theion concentration is not necessarily required to be uniform in the dopedlayer 32. For example, as depicted in FIG. 14, concentrations of ionsimplanted in the doped layer 32 can be changed for an overlapping region61 that overlaps the individual electrode 43 of the piezoelectricelement 44 and an outer peripheral region 62 that surrounds saidoverlapping region 61. Specifically, it is possible for concentration ofions implanted in the outer peripheral region 62 of the doped layer 32to be made higher than concentration of ions implanted in theoverlapping region 61 of the doped layer 32, and for the doped layer 32to be rendered electrically continuous with the common electrode 41 inthe outer peripheral region 62. By providing an outer side of thepiezoelectric element 44 with a region where ions have been implantedwith high concentration (the outer peripheral region 62), electrostaticnoise (ESD noise) from outside the ink-jet head 5 can be allowed toescape to the common electrode 41 via the outer peripheral region 62where the ions have been implanted with high concentration. As a result,misprinting or destruction of the piezoelectric element 44 due to ESDnoise from outside the ink-jet head 5 can be avoided.

In the previously described embodiment, the plurality of piezoelectricelements 44 were provided respectively corresponding to the plurality ofpressure chambers 26. The piezoelectric layer 42 and the individualelectrode 43 were separately provided to each of the piezoelectricelements 44. In contrast, the common electrode 41 was provided commonlyto all of the plurality of piezoelectric elements 44. The presentteaching is not limited to such a mode. The piezoelectric layer 42 maybe provided so as to straddle a plurality of the pressure chambers 26.For example, as depicted in FIG. 15, two piezoelectric layers 142 longin the conveyance direction may be formed corresponding to the twopressure chamber columns 27. Each of the piezoelectric layers 142extends in the conveyance direction so as to cover all of the pressurechambers 26 configuring one of the pressure chamber columns 27. Notethat a left end 142L and a right end 142R in the scanning direction ofthe piezoelectric layer 142 are respectively in the same positions asthe left end 42L and the right end 42R of the piezoelectric layer 42 inthe above-mentioned embodiment. Therefore, a description regarding thepositions of the left end 142L and the right end 142R will he omittedhere.

Although it is the case that the piezoelectric layer 142 is providedcommonly to the pressure chambers 26 configuring one pressure chambercolumn 27, one piezoelectric element 44 is configured with respect toone pressure chamber 26 by the individual electrode 43 and the commonelectrode 41 facing this one pressure chamber 26 and by a portionsandwiched by the individual electrode 43 and the common electrode 41,of the piezoelectric layer 142. Note that the piezoelectric layer 142need not be divided into two corresponding to the pressure chambercolumns 27, and it is possible for one piezoelectric layer to beprovided so as to cover all of the pressure chambers 26 of the twopressure chamber columns 27.

In the previously described embodiment, the plurality of pressurechambers 26 configured two pressure chamber columns 27, and thearrangement of the plurality of piezoelectric elements 44 was alsoconfigured as two columns in accordance with this arrangement of thepressure chambers 26. However, the number of columns of pressurechambers 26 or piezoelectric elements 44 is not limited to two, and maybe one, or may be three or more. Moreover, as depicted in FIGS. 7 and 8,the channel 29 joining the common liquid chamber 28 and the pressurechamber 26 is formed such that its width in the conveyance direction isnarrower than that of the pressure chamber 26. Note that a depth of thechannel 29 (a length in a thickness direction of the channel substrate21) was the same as a depth of the pressure chamber 26. However, thepresent teaching is not limited to such a mode. For example, the depthof the channel 29 may be configured so as to be smaller than the depthof the pressure chamber 26. In this case, the channel resistance of thechannel 29 can be made even larger and it is further suppressed that thepressure wave generated in the ink in the pressure chamber 26 escapes tothe common liquid chamber 28. Note that as mentioned above, the channel29 and the pressure chamber 26 are formed by etching the channelsubstrate 21. At this time, the depth of the channel 29 can be madeshallower than the depth of the pressure chamber 26 by adjusting a depthof etching.

In the above-described embodiment, the doped layer 32 covered above eachof the pressure chambers 26 so as to partition the entire upper surfaceof the pressure chamber 26. However, the present teaching is not limitedto such a configuration. It is possible for the doped layer 32 to beexposed in at least part of the pressure chamber 26 so that the dopedlayer 32 partitions part of the pressure chamber 26. In theabove-described embodiment, when forming the plurality of pressurechambers 26, the common liquid chamber 28, and the channels 29 byetching (refer to FIG. 13B), etching was performed on the channelsubstrate 21 to a depth that the doped layer 32 was exposed. However, itis possible for etching to be performed more deeply than to the depththat the doped layer 32 is exposed and for the doped layer 32 to beremoved and the insulating film 30 exposed. Even in this case, the dopedlayer 32 can be exposed in a stripe shape on a side surface of thepressure chamber 26. Therefore, when the inside of the pressure chamber26 has been filled with ink, the ink and the doped layer 32 can hebrought into contact with each other.

In the previously described embodiment, the conductive material disposedin the through hole 51 which is the hole for rendering electricallycontinuous the doped layer 32 and the common electrode 41, waselectrically continuous with the common electrode 41 by making directcontact with the common electrode 41. However, the conductive materialdisposed in the through hole 51 and the common electrode 41 do notnecessarily need to make direct contact. For example, the conductivematerial disposed in the through hole 51 and the common electrode 41 maybe in electrical contact via a wiring.

Moreover, in the previously described embodiment, the through hole 51which is the hole for rendering electrically continuous the doped layer32 and the common electrode 41 was formed in a position overlapping thepiezoelectric layer 42 in the up-down direction and between two channels29 in the conveyance direction. However, the position where the throughhole 51 is formed is not limited to the above-described position, and itmay be formed in any position of the insulating film 30. For example, itmay be formed between two pressure chambers 26 in the conveyancedirection, as in a through hole 251 depicted in FIG. 16. As a result ofthe through hole 51 being thus disposed in a position overlapping thepiezoelectric layer 42 in the up-down direction or in a positionsandwiched by two channels 29 in the conveyance direction or between twopressure chambers 26 in the conveyance direction, it becomes unnecessaryto secure a special region for providing the through holes 51, 251.Therefore, an increase in size of the head unit 16 can be suppressed.

Note that in the previously described embodiment, a plurality of thethrough holes 51 were provided corresponding to the number of pressurechambers 26. However, the number of through holes 51 is not limited tothat of the above-described embodiment, and may be set to any number.

In the previously described embodiment, when employing the ionimplanting apparatus to form the doped layer 32 after depositing theinsulating film 30 on the surface of the channel substrate 21, ions wereimplanted from a side of a surface where the insulating film 30 wasformed, of the channel substrate 21. Adjusting the accelerating voltageof the accelerator accelerating the ions makes it possible to adjust towhat depth the ions are implanted. Therefore, the ions do notnecessarily need to be implanted from the side of the surface where theinsulating film 30 is formed, of the channel substrate 21, and the ionsmay be implanted from a surface on an opposite side to the surface wherethe insulating film 30 is formed, of the channel substrate 21.

In the embodiment described above, the present teaching was applied tothe ink-jet head 5 that discharges ink onto a recording sheet to printan image or the like. In the above-described embodiment, the ink-jethead 5 was a so-called serial type ink-jet head, but the presentteaching is not limited to this and may be applied also to a so-calledline type ink-jet head. Moreover, the present teaching is not limited toan ink-jet head that discharges ink. The present teaching may be appliedalso to a liquid discharge apparatus used in a variety of applicationsbesides printing of an image or the like. For example, it is possible toapply the present teaching also to a liquid discharge apparatus thatdischarges a conductive liquid onto a substrate to form a conductivepattern on a substrate surface.

What is claimed is:
 1. A liquid discharge head comprising: asemiconductor substrate including a first pressure chamber; aninsulating film disposed above the first pressure chamber; and a firstpiezoelectric element disposed on an opposite side to the first pressurechamber of the insulating film, in a first direction in which the firstpressure chamber and the insulating film overlap, the firstpiezoelectric element including: a first electrode disposed above theinsulating film; a piezoelectric layer disposed above the firstelectrode; and a second electrode disposed above the piezoelectriclayer, wherein the semiconductor substrate further includes a dopedlayer, wherein the doped layer defines at least part of the firstpressure chamber, wherein the doped layer has a lower electricalresistivity than the insulating film and the semiconductor substrate,and wherein the insulating film includes a through hole in which aconductor is disposed, and the first electrode and the doped layer areelectrically connected to the conductor disposed in the through hole. 2.The liquid discharge head according to claim 1, wherein thesemiconductor substrate is a silicon substrate, and wherein theinsulating film is a silicon oxide film or a silicon nitride film. 3.The liquid discharge head according to claim 1, wherein the doped layeris disposed to cover at least part of a surface, of the first pressurechamber, facing the insulating film in the first direction.
 4. Theliquid discharge head according to claim 1, wherein the conductordisposed in the through hole is in direct contact with the firstelectrode so that the conductor is electrically connected to the firstelectrode.
 5. The liquid discharge head according to claim 1, whereinthe conductor disposed in the through hole is in direct contact with awiring extending from the first electrode so that the conductor iselectrically connected to the first electrode.
 6. The liquid dischargehead according to claim 1, wherein the semiconductor substrate includesa channel and a communicating chamber communicating with the firstpressure chamber via the channel, wherein the communicating chamber andthe first pressure chamber are separated in a second direction, andwherein the through hole is formed in the insulating film at a positionbetween the communicating chamber and the first pressure chamber in thesecond direction, the position being aligned with the channel in a thirddirection orthogonal to the second direction.
 7. The liquid dischargehead according to claim 1, wherein the doped layer comprises: a firstportion partitioning at least part of the first pressure chamber; and asecond portion disposed between the first portion and the conductor ofthe through hole, the second portion having a smaller electricalresistivity than the first portion.
 8. The liquid discharge headaccording to claim I., wherein the semiconductor substrate includes asecond pressure chamber adjacent to the first pressure chamber in afourth direction orthogonal to the first direction, wherein theinsulating film is disposed to cover the first pressure chamber and thesecond pressure chamber, wherein the liquid discharge head furthercomprises a second piezoelectric element disposed on an opposite side tothe second pressure chamber of the insulating film, in the firstdirection, wherein the second piezoelectric element includes a thirdelectrode connected to the first electrode of the first piezoelectricelement, and the through hole is disposed between the first pressurechamber and the second pressure chamber, of the insulating film, and iselectrically connected to the first electrode or the third electrode. 9.The liquid discharge head according to claim 1, wherein the through holeis formed in a position overlapping the piezoelectric layer in the firstdirection.
 10. A liquid discharge apparatus comprising: the liquiddischarge head as defined in claim 1; a conveyance mechanism configuredto convey a medium toward the liquid discharge head; and a tankconfigured to supply liquid to the liquid discharge head.